1. Field of the Invention
This invention relates to the field of information storage utilizing rigid disks, and more particularly to an apparatus and method for supporting read/write magnetic recording elements on a load beam having an integral flexure.
2. Description of the Prior Art
Magnetic head suspensions using a unitary load beam with an integral flexure for supporting a read/write head are well known in the prior art. U.S. Pat. No. 5,282,102 granted to Christianson discloses one such suspension. "Type 1650 Product Summary (Sep. 14, 1992)" published by Hutchinson Technology, Inc. of Hutchinson, Minn. also discloses another such suspension.
A prior art Hutchinson Technology Type 1650 suspension 100 (FIG. 1A) includes a lift rod 192 (shown in FIG. 1C), a load beam 101, and a flexure 110 supported by load beam surround portions 103 and 104. Flexure 110 is formed in load beam 101 by removing material to form slots 112, 114 and 116 and windows 122, 124, 126 and 128. Flexure 110 includes supports 132, 134, 136 and 138 which connect load beam surround portions 103 and 104 to roll elements 142 and 144 which in turn support an annular gimbal element 150. Gimbal element 150 is connected by pitch elements 152 and 154 to mounting pad 160 which supports a prior art air bearing slider 170 (FIG. 1B).
Air bearing slider 170 is a solid block with an air bearing side 171 and an opposing mounting side 172. Air bearing side 171 has a channel surface 175 separating a pair of rails 174A and 174B, each having a taper flat 176A and 176B adjacent front face 177. A magnetic read/write element 178 is mounted on a rear face 179 of air bearing slider 170. Mounting side 172 of air bearing slider 170 is a flat plane surface, which is illustrated in FIG. 1D.
When air bearing slider 170 is mounted on suspension 100, air bearing slider corners 184, 186 and 188 overlap load beam surround regions 103 and 104 (FIG. 1C). The overlaps are deliberately provided to act as limit stops during non-operational shock. Corner 180 of air bearing slider 170 may or may not be constrained by suspension 100 depending on how air bearing slider 170 is positioned when it is affixed to mounting pad 160. Referring to FIG. 1B, pitch (X-axis) and roll (Y-axis) angles are constrained to less than ten degrees in both directions by the limit stops at corners 184, 186 and 188. The stiffness of roll elements 142 and 144 and pitch elements 152 and 154 are kept high to constrain the Z-axis (see coordinate system 190 of FIG. 1B) motion of air bearing slider 170 during non-operational shock.
Previously, a separate flexure was required to support an air bearing slider. With the Type 1650 suspension, etching and forming are used to establish a clearance between the air bearing slider and the load beam surround portions in the following manner. Supports 132, 134, 136 and 138 slope out of the plane of load beam surround portions 103 and 104 so as to lift flexure 110 into a different plane. Roll elements 142 and 144 are supported by supports 132 and 134 (for roll element 142) and supports 136 and 138 (for roll element 144) in a plane at a distance t.sub.L =0.075 mm from the plane of load beam surround portions 103 and 104. Therefore, a nominal clearance C.sub.SL =0.075 mm is present between air bearing slider 170 and load beam surround portions 103 and 104 at air bearing slider corners 184, 186 and 188 shown in FIG. 1C.
Moreover, a portion of roll element 144 is etched away so that portion 144A (shown hatched in FIG. 1C) is thinner than portion 144B. For example, typical (but not absolute) dimensions used in the prior art are established by etching a load beam of thickness t.sub.L =0.075 mm down to a thickness t.sub.F =0.025 mm, results in a nominal clearance C.sub.AZ =t.sub.L -t.sub.F =0.050 mm between air bearing slider 170 and roll element 142A in the area 182 (FIGS. 1C and 1D and better shown in FIG. 1E). Roll element 142 is similar to roll element 144 and has portions 142A and 142B. Gimbal element 150 has the same thickness as portions 144A and 142A. The nominal clearances listed above are clearances with no load applied to air bearing slider 170.
Reduced thickness of flexure 110 increases the Z-axis compliance of air bearing slider 170 so that when air bearing slider 170 is loaded on the disk (flying above the surface of the disk on an air bearing), the suspension preload (typically 3 to 3.5 grams) reduces clearance C.sub.SL to less than 0.020 mm. Furthermore, clearance C.sub.AZ is reduced to less than 0.005 mm (due to compliance of flexure 110 in the Z-axis direction). With tolerances applied, interference can occur between roll element 142 and the edge of air bearing slider 170 in the region 182 (FIG. 1C). Any such interference moves the preload point forward relative to the center of pressure of air bearing surfaces of rails 174A and 174B, altering the flying characteristics of air bearing slider 170. In an extreme case, air bearing instability can result causing a head crash.
The interference problem (above) is further compounded by Z-axis shock loads. In the operating mode, if a shock occurs which loads suspension 100 towards the disk, the mass loading of suspension 100 results in a reduction in the clearance between air bearing slider 170 and load beam surround portions 103 and 104 (the effective mass of suspension 100 is approximately three times larger than the mass of air bearing slider 170). Impact at air bearing slider 170's corners 184, 186 and 188 can occur at shocks greater than 60 G's which can result in contact between a corner of air bearing surfaces 174A and 174B with the disk.
Interference problems can be reduced by increasing air bearing slider clearances C.sub.AZ and C.sub.SL. However, increased air bearing slider clearances require custom suspension design which in turn requires major retooling and expense.